Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF ...Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF envelope forming principle of spiral bevel gears is proposed.Secondly,the design methods for the envelope tool geometry and movement are proposed based on the envelope geometry and movement relationships.Thirdly,the metal flow and tooth filling laws are revealed through 3D FE simulation of the multi-DOF envelope forming process of a typical spiral bevel gear.Fourthly,a new method for separating the envelope tool and the formed spiral bevel gear with back taper tooth is proposed to avoid their interference.Finally,experiments on multi-DOF envelope forming of this typical spiral bevel gear are conducted using new heavy load multi-DOF envelope forming equipment.The simulation and experimental results show the feasibility of the proposed multi-DOF envelope forming process for fabricating spiral bevel gears with back taper tooth and the corresponding process design methods.展开更多
UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a f...UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a flight envelope constrained fixed-time control strategy is proposed to achieve a reliable UAV landing on a maneuvering ship.Firstly,a sliding data window autoregressive model is designed to predict the ship's roll and pitch motions,which are accordingly utilized to identify an appropriate quiescent period for safe landing.Subsequently,a barrier-function-based nonsingular terminal sliding mode controller is developed to eliminate the tracking errors within the identified quiescent period,while ensuring the errors remain bounded to satisfy flight envelope constraints.In particular,lumped disturbance components are estimated by integrating a fixed-time disturbance observer and compensated in the controller.The key advantage of the proposed approach is that it well balances the control requirements between precise landing position and safe landing attitude,guaranteeing both steady-state performance and transient behavior of the tracking error.Finally,comparative Gazebo simulations in different sea state scenarios are conducted to verify the satisfactory control performance.展开更多
The stratospheric airship is affected by harsh conditions in the stratosphere environment.To ensure the safety of the airship,it is necessary to detect the material state of the airship envelope.Since digital image co...The stratospheric airship is affected by harsh conditions in the stratosphere environment.To ensure the safety of the airship,it is necessary to detect the material state of the airship envelope.Since digital image correlation possesses non-contact strain measurement ability,this paper explores the infuence of different shapes of the subset on measurement accuracy.Through the results,it is found that increasing the aspect ratio of subsets can improve the strain accuracy measured in the c-direction,and reducing the aspect ratio can improve the strain accuracy measured in the y-direction.This trend becomes more obvious as the strain increases.Based on this discovery,a subset adaptive algorithm is proposed.The feasibility of the algorithm is verified by experiments,and the precision of strain measurement can be effectively improved by adjusting the threshold value.Therefore,the algorithm can be utilized to increase the measurement accuracy in the larger strain direction without changing the size of the subset.展开更多
The circumstellar envelopes(CSE) of asymptotic giant branch(AGB) stars are abundant in molecular emissions, offering valuable insights into the physical and chemical conditions of these evolving stars. In this paper, ...The circumstellar envelopes(CSE) of asymptotic giant branch(AGB) stars are abundant in molecular emissions, offering valuable insights into the physical and chemical conditions of these evolving stars. In this paper, we report observations of two molecules(CO and SO_(2)) toward four O-rich AGB stars using the James Clerk Maxwell Telescope(JCMT). We detected an unusual SO_(2) spectral feature comprising both broad and narrow components in IK Tau and AP Lyn. The broad line profiles may originate from thermal molecular emission, while the narrow profiles could come from other species(or masers) or astrophysical phenomena occurring within the CSEs of the AGB stars, such as episodic mass loss, bipolar outflows, or emissions associated with the complex physical processes near the central star. The narrow lines of SO_(2) may also arise from vibrationally excited emissions. Additionally, we observed the same U-line in both TX Cam and IK Tau, which may originate from the molecule N^(17)O. We analyzed the identified molecular lines using rotational diagrams to determine their excitation temperatures, column densities, and fractional abundances. This information aids in the constructing of reliable astrochemical models for a more detailed examination of the target stars. The narrow component of the SO_(2) line suggests unusual astrophysical phenomena, making IK Tau and AP Lyn particularly intriguing for further investigation to fully understand the physical processes at play in these sources.展开更多
It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate ...It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.展开更多
Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,...Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.展开更多
The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and f...The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering components.By contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,respectively.Hence,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity problem.In this study,we conducted a trial application of the envelope method to the potential ambiguity problem.The envelope method was improved by including uncertainties in the experimental data.The colliding systems of 16O+28Si at 215.2 MeV and 12C+12C at 1016 MeV were considered in the analyses.For each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is refractive.The calculated angular distributions were decomposed into nearside and farside scattering components.Using the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside components.The capability of the envelope method to analyze the potential ambiguities was also discussed.展开更多
The development of machine learning technology enables more robust real-time earthquake monitoring through automated implementations. However, the application of machine learning to earthquake location problems faces ...The development of machine learning technology enables more robust real-time earthquake monitoring through automated implementations. However, the application of machine learning to earthquake location problems faces challenges in regions with limited available training data. To address the issues of sparse event distribution and inaccurate ground truth in historical seismic datasets, we expand the training dataset by using a large number of synthetic envelopes that closely resemble real data and build an earthquake location model named ENVloc. We propose an envelope-based machine learning workflow for simultaneously determining earthquake location and origin time. The method eliminates the need for phase picking and avoids the accumulation of location errors resulting from inaccurate picking results. In practical application, ENVloc is applied to several data intercepted at different starting points. We take the starting point of the time window corresponding to the highest prediction probability value as the origin time and save the predicted result as the earthquake location. We apply ENVloc to observed data acquired in the southern Sichuan Basin, China, between September 2018 and March 2019. The results show that the average difference with the catalog in latitude, longitude, depth, and origin time is 0.02°,0.02°, 2 km, and 1.25 s, respectively. These suggest that our envelope-based method provides an efficient and robust way to locate earthquakes without phase picking, and can be used in earthquake monitoring in near-real time.展开更多
BACKGROUND Occult hepatitis B infection(OBI)is characterized by the detection of hepatitis B virus(HBV)DNA in serum(usually HBV DNA<200 IU/mL)or the liver but negativity for hepatitis B surface antigen(HBsAg).The d...BACKGROUND Occult hepatitis B infection(OBI)is characterized by the detection of hepatitis B virus(HBV)DNA in serum(usually HBV DNA<200 IU/mL)or the liver but negativity for hepatitis B surface antigen(HBsAg).The diagnosis of OBI relies on the sensitivity of assays used in the detection of HBV DNA and HBsAg.HBsAg assays with inadequate sensitivity or inability to detect HBV S variants may lead to misdiagnosis of OBI in people with overt HBV infection.CASE SUMMARY We report a HBsAg-negative but hepatitis B envelope antigen-positive patient who had a significant HBV DNA level.The patient was initially diagnosed as having OBI.However,sequence analysis revealed a unique insertion of amino acid residues at positions 120-124 in the S protein,which affects the formation of a disulfide bond that is associated with the formation of a loop.It is well known that there is an overlap between the S protein and Pol protein.We found that this new insertion site occurred in polymerase/reverse transcriptase domain,indi-cating that this insertion might be involved in HBV pathogenicity.The patient was finally diagnosed with a false OBI.CONCLUSION An insertion of amino acid residues at positions 120-124 of the S protein affects the formation of immunodominant epitopes and results in negative HBsAg levels.展开更多
In the data envelopment analysis(DEA)literature,productivity change captured by the Malmquist productivity index,especially in terms of a deterministic environment and stochastic variability in inputs and outputs,has ...In the data envelopment analysis(DEA)literature,productivity change captured by the Malmquist productivity index,especially in terms of a deterministic environment and stochastic variability in inputs and outputs,has been somewhat ignored.Therefore,this study developed a firm-specific,DEA-based Malmquist index model to examine the efficiency and productivity change of banks in a stochastic environment.First,in order to estimate bank-specific efficiency,we employed a two-stage double bootstrap DEA procedure.Specifically,in the first stage,the technical efficiency scores of banks were calculated by the classic DEA model,while in the second stage,the double bootstrap DEA model was applied to determine the effect of the contextual variables on bank efficiency.Second,we applied a two-stage procedure for measuring productivity change in which the first stage included the estimation of stochastic technical efficiency and the second stage included the regression of the estimated efficiency scores on a set of explanatory variables that influence relative performance.Finally,an empirical investigation of the Iranian banking sector,consisting of 120 bank-year observations of 15 banks from 2014 to 2021,was performed to measure their efficiency and productivity change.Based on the findings,the explanatory variables(i.e.,the nonperforming loan ratio and the number of branches)indicated an inverse relationship with stochastic technical efficiency and productivity change.The implication of the findings is that,in order to improve the efficiency and productivity of banks,it is important to optimize these factors.展开更多
Fine structure and elemental composition of envelopes of 10 taxa of Trachelomonas and Strombomonas from natural freshwater bodies in China were studied and phylogeny of both genera were discussed. The results indicate...Fine structure and elemental composition of envelopes of 10 taxa of Trachelomonas and Strombomonas from natural freshwater bodies in China were studied and phylogeny of both genera were discussed. The results indicate that iron (Fe) and silicon (Si) are the primary mineral elements of the envelopes. Composition of mineral elements was uncorrelated with envelope color, however, it was highly correlated with the microarchitecture of the envelopes. Content of Si was higher than that of Fe in all species of Strombomonas and some species of Trachelomonas with rough surface. In most species of Trachelomonas, especially those with dense and smoothy surface, content of Fe was higher than that of Si. Based on the above results, we propose to assign those species of Strombomonas into Trachelomonas and consider them as a group of the latter. These species were the most primitive among the group with envelopes in Euglenaceae.展开更多
The absence of low-frequency information in seismic data is one of the most difficult problems in elastic full waveform inversion. Without low-frequency data, it is difficult to recover the long-wavelength components ...The absence of low-frequency information in seismic data is one of the most difficult problems in elastic full waveform inversion. Without low-frequency data, it is difficult to recover the long-wavelength components of subsurface models and the inversion converges to local minima. To solve this problem, the elastic envelope inversion method is introduced. Based on the elastic envelope operator that is capable of retrieving low- frequency signals hidden in multicomponent data, the proposed method uses the envelope of multicomponent seismic signals to construct a misfit function and then recover the long- wavelength components of the subsurface model. Numerical tests verify that the elastic envelope method reduces the inversion nonlinearity and provides better starting models for the subsequent conventional elastic full waveform inversion and elastic depth migration, even when low frequencies are missing in multicomponent data and the starting model is far from the true model. Numerical tests also suggest that the proposed method is more effective in reconstructing the long-wavelength components of the S-wave velocity model. The inversion of synthetic data based on the Marmousi-2 model shows that the resolution of conventional elastic full waveform inversion improves after using the starting model obtained using the elastic envelope method. Finally, the limitations of the elastic envelope inversion method are discussed.展开更多
As in homology, the notion of injectivity is introduced in the category whose objects are Hilbert C * module over a C * algebra and whose morphism are bounded module operators. The definition of injective envelope...As in homology, the notion of injectivity is introduced in the category whose objects are Hilbert C * module over a C * algebra and whose morphism are bounded module operators. The definition of injective envelopes of an extension of a Hilbert C * modules over a C * algebra is introduced, and is characterized in terms of the injectivity and essence. It is shown that every Hilbert C * module has a unique (up to H isometrics) injective envelope if it exists. It is also shown that an extension of a Hilbert C * module is an injective envelope if and only if it is an injective and essential extension. Moreover, every Hilbert C * module over a W * algebra has a unique (up to H isometrics) injective envelope and the injective envelope of a Hilbert C * module H is maximal essential extension of H .展开更多
Let H be a Hopf algebra and HYD the Yetter- Drinfeld category over H. First, the enveloping algebra of generalized H-Hom-Lie algebra L, i.e., Hom-Lie algebra L H in the category HYD, is constructed. Secondly, it is o...Let H be a Hopf algebra and HYD the Yetter- Drinfeld category over H. First, the enveloping algebra of generalized H-Hom-Lie algebra L, i.e., Hom-Lie algebra L H in the category HYD, is constructed. Secondly, it is obtained that U（L） = T（ L）/L where I is the Hom-ideal of T（L） generated by {ll＇-l_（（-1））·l＇l_0-[l,l＇]｜l,l＇∈L}, and u： L,T（L）/I is the canonical map. Finally, as the applications of the result, the enveloping algebras of generalized H-Lie algebras, i.e., the Lie algebras in the category MyDn and the Hom-Lie algebras in the category of left H-comodules are presented, respectively.展开更多
In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problema...In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problematic in several situations,for example(a)when input proportions change in the long run,(b)when inputs are heterogeneous,and(c)when firms face ex-ante price uncertainty in making their production decisions.To address these situations,a scale elasticity evaluation was performed using a value-based cost efficiency model.However,this alternative value-based scale elasticity evaluation is sensitive to the uncertainty and variability underlying input and output data.Therefore,in this study,we introduce a stochastic cost-efficiency model based on chance-constrained programming to develop a value-based measure of the scale elasticity of firms facing data uncertainty.An illustrative empirical application to the Indian banking industry comprising 71 banks for eight years(1998–2005)was made to compare inferences about their efficiency and scale properties.The key findings are as follows:First,both the deterministic model and our proposed stochastic model yield distinctly different results concerning the efficiency and scale elasticity scores at various tolerance levels of chance constraints.However,both models yield the same results at a tolerance level of 0.5,implying that the deterministic model is a special case of the stochastic model in that it reveals the same efficiency and returns to scale characterizations of banks.Second,the stochastic model generates higher efficiency scores for inefficient banks than its deterministic counterpart.Third,public banks exhibit higher efficiency than private and foreign banks.Finally,public and old private banks mostly exhibit either decreasing or constant returns to scale,whereas foreign and new private banks experience either increasing or decreasing returns to scale.Although the application of our proposed stochastic model is illustrative,it can be potentially applied to all firms in the information and distribution-intensive industry with high fixed costs,which have ample potential for reaping scale and scope benefits.展开更多
The Shipboard Operation Envelope(SOE) is the safe boundary of the helicopter/ship dynamic interface. The night deck on a ship is usually behind the hangar, where the airflow is turbulent due to the influence of the up...The Shipboard Operation Envelope(SOE) is the safe boundary of the helicopter/ship dynamic interface. The night deck on a ship is usually behind the hangar, where the airflow is turbulent due to the influence of the upper structure, wind and ship speed. The turbulent airnow is the major adverse factor for the safety of shipboard operations. In this paper, the night deck abbot is analysed as the superposition of two penyndicular 2-D airflows.N-S equations are used to calculate the velocity field and the range of turbulent airflow using finite element method. The result is correspondent well with test. Incorporating the influence of the airflow and giving some restrictions on the movements of the ship and on the control margin of the helicopter, the operation envelopes are calculated. The operation envelopes include three types for hovering over the deck, taking-off from and landing on ship, and landing with a landing-aid system. These results are helpful to the pilot training and night safety.展开更多
Objective To evaluate the environmental and technical efficiencies of China＇s industrial sectors and provide appropriate advice for policy makers in the context of rapid economic growth and concurrent serious environ...Objective To evaluate the environmental and technical efficiencies of China＇s industrial sectors and provide appropriate advice for policy makers in the context of rapid economic growth and concurrent serious environmental damages caused by industrial pollutants. Methods A data of envelopment analysis （DEA） framework crediting both reduction of pollution outputs and expansion of good outputs was designed as a model to compute environmental efficiency of China＇s regional industrial systems. Results As shown by the geometric mean of environmental efficiency, if other inputs were made constant and good outputs were not to be improved, the air pollution outputs would have the potential to be decreased by about 60% in the whole China. Conclusion Both environmental and technical efficiencies have the potential to be greatly improved in China, which may provide some advice for policy-makers.展开更多
Envelope analysis is an effective method for characterizing impulsive vibrations in wired condition monitoring(CM)systems. This paper depicts the implementation of envelope analysis on a wireless sensor node for obtai...Envelope analysis is an effective method for characterizing impulsive vibrations in wired condition monitoring(CM)systems. This paper depicts the implementation of envelope analysis on a wireless sensor node for obtaining a more convenient and reliable CM system. To maintain CM performances under the constraints of resources available in the cost effective Zigbee based wireless sensor network(WSN), a low cost cortex-M4 F microcontroller is employed as the core processor to implement the envelope analysis algorithm on the sensor node. The on-chip 12 bit analog-to-digital converter(ADC) working at 10 k Hz sampling rate is adopted to acquire vibration signals measured by a wide frequency band piezoelectric accelerometer. The data processing flow inside the processor is optimized to satisfy the large memory usage in implementing fast Fourier transform(FFT) and Hilbert transform(HT). Thus, the envelope spectrum can be computed from a data frame of 2048 points to achieve a frequency resolution acceptable for identifying the characteristic frequencies of different bearing faults. Experimental evaluation results show that the embedded envelope analysis algorithm can successfully diagnose the simulated bearing faults and the data transmission throughput can be reduced by at least 95% per frame compared with that of the raw data, allowing a large number of sensor nodes to be deployed in the network for real time monitoring.展开更多
The conventional data envelopment analysis （DEA） measures the relative efficiencies of a set of decision making units with exact values of inputs and outputs. In real-world prob- lems, however, inputs and outputs ty...The conventional data envelopment analysis （DEA） measures the relative efficiencies of a set of decision making units with exact values of inputs and outputs. In real-world prob- lems, however, inputs and outputs typically have some levels of fuzziness. To analyze a decision making unit （DMU） with fuzzy input/output data, previous studies provided the fuzzy DEA model and proposed an associated evaluating approach. Nonetheless, numerous deficiencies must still be improved, including the α- cut approaches, types of fuzzy numbers, and ranking techniques. Moreover, a fuzzy sample DMU still cannot be evaluated for the Fuzzy DEA model. Therefore, this paper proposes a fuzzy DEA model based on sample decision making unit （FSDEA）. Five eval- uation approaches and the related algorithm and ranking methods are provided to test the fuzzy sample DMU of the FSDEA model. A numerical experiment is used to demonstrate and compare the results with those obtained using alternative approaches.展开更多
The cylindrical worm processed by annular grinding wheel envelope in two degree of freedom motion state is a novel worm. This paper explains the shaping principle of such a worm. To improve meshing quality and the p...The cylindrical worm processed by annular grinding wheel envelope in two degree of freedom motion state is a novel worm. This paper explains the shaping principle of such a worm. To improve meshing quality and the properties of contact and lubrication, the multi objective optimization has been conducted for the first time to the parameters of such a worm pair by the fuzzy optimal method. The results show that, the shape of the contact line is visibly more sloped than before being optimized, lubrication angle is apparently bigger, and the distribution of contact lines is much improved.展开更多
基金the National Science and Technology Major Project of China(No.2019-VII0017e0158)the National Natural Science Foundation of China(No.U21A20131)+1 种基金the Industry-University Research Cooperation Project,China(No.HFZL2020CXY025)the National Key Laboratory of Science and Technology on Helicopter Transmission,China(No.HTL-O-21G05).
文摘Spiral bevel gears are critical transmission components,and are widely used in the aerospace field.This paper proposes a new multi-DOF envelope forming process for fabricating spiral bevel gears.Firstly,the multi-DOF envelope forming principle of spiral bevel gears is proposed.Secondly,the design methods for the envelope tool geometry and movement are proposed based on the envelope geometry and movement relationships.Thirdly,the metal flow and tooth filling laws are revealed through 3D FE simulation of the multi-DOF envelope forming process of a typical spiral bevel gear.Fourthly,a new method for separating the envelope tool and the formed spiral bevel gear with back taper tooth is proposed to avoid their interference.Finally,experiments on multi-DOF envelope forming of this typical spiral bevel gear are conducted using new heavy load multi-DOF envelope forming equipment.The simulation and experimental results show the feasibility of the proposed multi-DOF envelope forming process for fabricating spiral bevel gears with back taper tooth and the corresponding process design methods.
文摘UAV shipboard landing poses significant challenges in terms of safety and efficiency,due to the oscillatory ship motion caused by wave interactions and wind gusts,especially in rough sea states.To solve this issue,a flight envelope constrained fixed-time control strategy is proposed to achieve a reliable UAV landing on a maneuvering ship.Firstly,a sliding data window autoregressive model is designed to predict the ship's roll and pitch motions,which are accordingly utilized to identify an appropriate quiescent period for safe landing.Subsequently,a barrier-function-based nonsingular terminal sliding mode controller is developed to eliminate the tracking errors within the identified quiescent period,while ensuring the errors remain bounded to satisfy flight envelope constraints.In particular,lumped disturbance components are estimated by integrating a fixed-time disturbance observer and compensated in the controller.The key advantage of the proposed approach is that it well balances the control requirements between precise landing position and safe landing attitude,guaranteeing both steady-state performance and transient behavior of the tracking error.Finally,comparative Gazebo simulations in different sea state scenarios are conducted to verify the satisfactory control performance.
文摘The stratospheric airship is affected by harsh conditions in the stratosphere environment.To ensure the safety of the airship,it is necessary to detect the material state of the airship envelope.Since digital image correlation possesses non-contact strain measurement ability,this paper explores the infuence of different shapes of the subset on measurement accuracy.Through the results,it is found that increasing the aspect ratio of subsets can improve the strain accuracy measured in the c-direction,and reducing the aspect ratio can improve the strain accuracy measured in the y-direction.This trend becomes more obvious as the strain increases.Based on this discovery,a subset adaptive algorithm is proposed.The feasibility of the algorithm is verified by experiments,and the precision of strain measurement can be effectively improved by adjusting the threshold value.Therefore,the algorithm can be utilized to increase the measurement accuracy in the larger strain direction without changing the size of the subset.
基金support from the Natural Science Foundation of Xinjiang Uygur Autonomous Region, China (Grant No. 2024D01E37)the National Natural Science Foundation of China (Grant No. 12473025)+5 种基金supported by grant number ST/T000198/1 from the STFCthe sponsored by Natural Science Foundation of Xinjiang Uygur Autonomous Region, China (Grant No. 2022D01B221)the Xinjiang Tianchi Talent Project (2019)The James Clerk Maxwell Telescope is operated by the East Asian Observatory on behalf of the National Astronomical Observatory of Japan, Academia Sinica Institute of Astronomy and Astrophysics, the Korea Astronomy and Space Science Institute, the National Astronomical Research Institute of Thailand, Center for Astronomical Mega-Science as well as the National Key Research and Development Program of China (Grant No. 2017YFA0402700)support is provided by the Science and Technology Facilities Council of the United Kingdom and participating universities and organizations in the United Kingdom and Canadasupported by the JCMT M22BP013 project。
文摘The circumstellar envelopes(CSE) of asymptotic giant branch(AGB) stars are abundant in molecular emissions, offering valuable insights into the physical and chemical conditions of these evolving stars. In this paper, we report observations of two molecules(CO and SO_(2)) toward four O-rich AGB stars using the James Clerk Maxwell Telescope(JCMT). We detected an unusual SO_(2) spectral feature comprising both broad and narrow components in IK Tau and AP Lyn. The broad line profiles may originate from thermal molecular emission, while the narrow profiles could come from other species(or masers) or astrophysical phenomena occurring within the CSEs of the AGB stars, such as episodic mass loss, bipolar outflows, or emissions associated with the complex physical processes near the central star. The narrow lines of SO_(2) may also arise from vibrationally excited emissions. Additionally, we observed the same U-line in both TX Cam and IK Tau, which may originate from the molecule N^(17)O. We analyzed the identified molecular lines using rotational diagrams to determine their excitation temperatures, column densities, and fractional abundances. This information aids in the constructing of reliable astrochemical models for a more detailed examination of the target stars. The narrow component of the SO_(2) line suggests unusual astrophysical phenomena, making IK Tau and AP Lyn particularly intriguing for further investigation to fully understand the physical processes at play in these sources.
文摘It is now recognized that many geomaterials have nonlinear failure envelopes. This non-linearity is most marked at lower stress levels, the failure envelope being of quasi-parabolic shape. It is not easy to calibrate these nonlinear failure envelopes from triaxial test data. Currently only the power-type failure envelope has been studied with an established formal procedure for its determination from triaxial test data. In this paper, a simplified procedure is evolved for the development of four different types of nonlinear envelopes. These are of invaluable assistance in the evaluation of true factors of safety in problems of slope stability and correct computation of lateral earth pressure and bearing capacity. The use of the Mohr-Coulomb failure envelopes leads to an overestimation of the factors of safety and other geotechnical quantities.
基金supported by the National Natural Science Foundation of China(52078269 and 52325801).
文摘Substantially glazed facades are extensively used in contemporary high-rise buildings to achieve attractive architectural aesthetics.Inherent conflicts exist among architectural aesthetics,building energy consumption,and solar energy harvesting for glazed facades.In this study,we addressed these conflicts by introducing a new dynamic and vertical photovoltaic integrated building envelope(dvPVBE)that offers extraordinary flexibility with weather-responsive slat angles and blind positions,superior architectural aesthetics,and notable energy-saving potential.Three hierarchical control strategies were proposed for different scenarios of the dvPVBE:power generation priority(PGP),natural daylight priority(NDP),and energy-saving priority(ESP).Moreover,the PGP and ESP strategies were further analyzed in the simulation of a dvPVBE.An office room integrated with a dvPVBE was modeled using EnergyPlus.The influence of the dvPVBE in improving the building energy efficiency and corresponding optimal slat angles was investigated under the PGP and ESP control strategies.The results indicate that the application of dvPVBEs in Beijing can provide up to 131%of the annual energy demand of office rooms and significantly increase the annual net energy output by at least 226%compared with static photovoltaic(PV)blinds.The concept of this novel dvPVBE offers a viable approach by which the thermal load,daylight penetration,and energy generation can be effectively regulated.
基金This work was supported by the National Natural Science Foundation of China(Nos.12005047 and U1832105).
文摘The optical potential ambiguity is a long-standing problem in the analysis of elastic scattering data.For a specific collid-ing system,ambiguous potential families can lead to different behaviors in the nearside and farside scattering components.By contrast,the envelope method can decompose the experimental data into two components with negative and positive deflection angles,respectively.Hence,a question arises as to whether the comparison between the calculated nearside(or farside)component and the derived positive-deflection-angle(or negative-deflection-angle)component can help analyze the potential ambiguity problem.In this study,we conducted a trial application of the envelope method to the potential ambiguity problem.The envelope method was improved by including uncertainties in the experimental data.The colliding systems of 16O+28Si at 215.2 MeV and 12C+12C at 1016 MeV were considered in the analyses.For each colliding system,the angular distribution experimental data were described nearly equally well by two potential sets,one of which is“surface transpar-ent”and the other is refractive.The calculated angular distributions were decomposed into nearside and farside scattering components.Using the improved envelope method,the experimental data were decomposed into the positive-deflection-angle and negative-deflection-angle components,which were then compared with the calculated nearside and farside components.The capability of the envelope method to analyze the potential ambiguities was also discussed.
基金the financial support of the National Key R&D Program of China(2021YFC3000701)the China Seismic Experimental Site in Sichuan-Yunnan(CSES-SY)for providing data for this study.
文摘The development of machine learning technology enables more robust real-time earthquake monitoring through automated implementations. However, the application of machine learning to earthquake location problems faces challenges in regions with limited available training data. To address the issues of sparse event distribution and inaccurate ground truth in historical seismic datasets, we expand the training dataset by using a large number of synthetic envelopes that closely resemble real data and build an earthquake location model named ENVloc. We propose an envelope-based machine learning workflow for simultaneously determining earthquake location and origin time. The method eliminates the need for phase picking and avoids the accumulation of location errors resulting from inaccurate picking results. In practical application, ENVloc is applied to several data intercepted at different starting points. We take the starting point of the time window corresponding to the highest prediction probability value as the origin time and save the predicted result as the earthquake location. We apply ENVloc to observed data acquired in the southern Sichuan Basin, China, between September 2018 and March 2019. The results show that the average difference with the catalog in latitude, longitude, depth, and origin time is 0.02°,0.02°, 2 km, and 1.25 s, respectively. These suggest that our envelope-based method provides an efficient and robust way to locate earthquakes without phase picking, and can be used in earthquake monitoring in near-real time.
基金Supported by the Shanghai Municipal Commission of Health and Family Planning,No.PKJ2018-Y05.
文摘BACKGROUND Occult hepatitis B infection(OBI)is characterized by the detection of hepatitis B virus(HBV)DNA in serum(usually HBV DNA<200 IU/mL)or the liver but negativity for hepatitis B surface antigen(HBsAg).The diagnosis of OBI relies on the sensitivity of assays used in the detection of HBV DNA and HBsAg.HBsAg assays with inadequate sensitivity or inability to detect HBV S variants may lead to misdiagnosis of OBI in people with overt HBV infection.CASE SUMMARY We report a HBsAg-negative but hepatitis B envelope antigen-positive patient who had a significant HBV DNA level.The patient was initially diagnosed as having OBI.However,sequence analysis revealed a unique insertion of amino acid residues at positions 120-124 in the S protein,which affects the formation of a disulfide bond that is associated with the formation of a loop.It is well known that there is an overlap between the S protein and Pol protein.We found that this new insertion site occurred in polymerase/reverse transcriptase domain,indi-cating that this insertion might be involved in HBV pathogenicity.The patient was finally diagnosed with a false OBI.CONCLUSION An insertion of amino acid residues at positions 120-124 of the S protein affects the formation of immunodominant epitopes and results in negative HBsAg levels.
文摘In the data envelopment analysis(DEA)literature,productivity change captured by the Malmquist productivity index,especially in terms of a deterministic environment and stochastic variability in inputs and outputs,has been somewhat ignored.Therefore,this study developed a firm-specific,DEA-based Malmquist index model to examine the efficiency and productivity change of banks in a stochastic environment.First,in order to estimate bank-specific efficiency,we employed a two-stage double bootstrap DEA procedure.Specifically,in the first stage,the technical efficiency scores of banks were calculated by the classic DEA model,while in the second stage,the double bootstrap DEA model was applied to determine the effect of the contextual variables on bank efficiency.Second,we applied a two-stage procedure for measuring productivity change in which the first stage included the estimation of stochastic technical efficiency and the second stage included the regression of the estimated efficiency scores on a set of explanatory variables that influence relative performance.Finally,an empirical investigation of the Iranian banking sector,consisting of 120 bank-year observations of 15 banks from 2014 to 2021,was performed to measure their efficiency and productivity change.Based on the findings,the explanatory variables(i.e.,the nonperforming loan ratio and the number of branches)indicated an inverse relationship with stochastic technical efficiency and productivity change.The implication of the findings is that,in order to improve the efficiency and productivity of banks,it is important to optimize these factors.
文摘Fine structure and elemental composition of envelopes of 10 taxa of Trachelomonas and Strombomonas from natural freshwater bodies in China were studied and phylogeny of both genera were discussed. The results indicate that iron (Fe) and silicon (Si) are the primary mineral elements of the envelopes. Composition of mineral elements was uncorrelated with envelope color, however, it was highly correlated with the microarchitecture of the envelopes. Content of Si was higher than that of Fe in all species of Strombomonas and some species of Trachelomonas with rough surface. In most species of Trachelomonas, especially those with dense and smoothy surface, content of Fe was higher than that of Si. Based on the above results, we propose to assign those species of Strombomonas into Trachelomonas and consider them as a group of the latter. These species were the most primitive among the group with envelopes in Euglenaceae.
文摘The absence of low-frequency information in seismic data is one of the most difficult problems in elastic full waveform inversion. Without low-frequency data, it is difficult to recover the long-wavelength components of subsurface models and the inversion converges to local minima. To solve this problem, the elastic envelope inversion method is introduced. Based on the elastic envelope operator that is capable of retrieving low- frequency signals hidden in multicomponent data, the proposed method uses the envelope of multicomponent seismic signals to construct a misfit function and then recover the long- wavelength components of the subsurface model. Numerical tests verify that the elastic envelope method reduces the inversion nonlinearity and provides better starting models for the subsequent conventional elastic full waveform inversion and elastic depth migration, even when low frequencies are missing in multicomponent data and the starting model is far from the true model. Numerical tests also suggest that the proposed method is more effective in reconstructing the long-wavelength components of the S-wave velocity model. The inversion of synthetic data based on the Marmousi-2 model shows that the resolution of conventional elastic full waveform inversion improves after using the starting model obtained using the elastic envelope method. Finally, the limitations of the elastic envelope inversion method are discussed.
文摘As in homology, the notion of injectivity is introduced in the category whose objects are Hilbert C * module over a C * algebra and whose morphism are bounded module operators. The definition of injective envelopes of an extension of a Hilbert C * modules over a C * algebra is introduced, and is characterized in terms of the injectivity and essence. It is shown that every Hilbert C * module has a unique (up to H isometrics) injective envelope if it exists. It is also shown that an extension of a Hilbert C * module is an injective envelope if and only if it is an injective and essential extension. Moreover, every Hilbert C * module over a W * algebra has a unique (up to H isometrics) injective envelope and the injective envelope of a Hilbert C * module H is maximal essential extension of H .
基金The National Natural Science Foundation of China(No.11371088)the Excellent Young Talents Fund of Anhui Province(No.2013SQRL092ZD)+2 种基金the Natural Science Foundation of Higher Education Institutions of Anhui Province(No.KJ2015A294)China Postdoctoral Science Foundation(No.2015M571725)the Excellent Young Talents Fund of Chuzhou University(No.2013RC001)
文摘Let H be a Hopf algebra and HYD the Yetter- Drinfeld category over H. First, the enveloping algebra of generalized H-Hom-Lie algebra L, i.e., Hom-Lie algebra L H in the category HYD, is constructed. Secondly, it is obtained that U（L） = T（ L）/L where I is the Hom-ideal of T（L） generated by {ll＇-l_（（-1））·l＇l_0-[l,l＇]｜l,l＇∈L}, and u： L,T（L）/I is the canonical map. Finally, as the applications of the result, the enveloping algebras of generalized H-Lie algebras, i.e., the Lie algebras in the category MyDn and the Hom-Lie algebras in the category of left H-comodules are presented, respectively.
文摘In the nonparametric data envelopment analysis literature,scale elasticity is evaluated in two alternative ways:using either the technical efficiency model or the cost efficiency model.This evaluation becomes problematic in several situations,for example(a)when input proportions change in the long run,(b)when inputs are heterogeneous,and(c)when firms face ex-ante price uncertainty in making their production decisions.To address these situations,a scale elasticity evaluation was performed using a value-based cost efficiency model.However,this alternative value-based scale elasticity evaluation is sensitive to the uncertainty and variability underlying input and output data.Therefore,in this study,we introduce a stochastic cost-efficiency model based on chance-constrained programming to develop a value-based measure of the scale elasticity of firms facing data uncertainty.An illustrative empirical application to the Indian banking industry comprising 71 banks for eight years(1998–2005)was made to compare inferences about their efficiency and scale properties.The key findings are as follows:First,both the deterministic model and our proposed stochastic model yield distinctly different results concerning the efficiency and scale elasticity scores at various tolerance levels of chance constraints.However,both models yield the same results at a tolerance level of 0.5,implying that the deterministic model is a special case of the stochastic model in that it reveals the same efficiency and returns to scale characterizations of banks.Second,the stochastic model generates higher efficiency scores for inefficient banks than its deterministic counterpart.Third,public banks exhibit higher efficiency than private and foreign banks.Finally,public and old private banks mostly exhibit either decreasing or constant returns to scale,whereas foreign and new private banks experience either increasing or decreasing returns to scale.Although the application of our proposed stochastic model is illustrative,it can be potentially applied to all firms in the information and distribution-intensive industry with high fixed costs,which have ample potential for reaping scale and scope benefits.
文摘The Shipboard Operation Envelope(SOE) is the safe boundary of the helicopter/ship dynamic interface. The night deck on a ship is usually behind the hangar, where the airflow is turbulent due to the influence of the upper structure, wind and ship speed. The turbulent airnow is the major adverse factor for the safety of shipboard operations. In this paper, the night deck abbot is analysed as the superposition of two penyndicular 2-D airflows.N-S equations are used to calculate the velocity field and the range of turbulent airflow using finite element method. The result is correspondent well with test. Incorporating the influence of the airflow and giving some restrictions on the movements of the ship and on the control margin of the helicopter, the operation envelopes are calculated. The operation envelopes include three types for hovering over the deck, taking-off from and landing on ship, and landing with a landing-aid system. These results are helpful to the pilot training and night safety.
文摘Objective To evaluate the environmental and technical efficiencies of China＇s industrial sectors and provide appropriate advice for policy makers in the context of rapid economic growth and concurrent serious environmental damages caused by industrial pollutants. Methods A data of envelopment analysis （DEA） framework crediting both reduction of pollution outputs and expansion of good outputs was designed as a model to compute environmental efficiency of China＇s regional industrial systems. Results As shown by the geometric mean of environmental efficiency, if other inputs were made constant and good outputs were not to be improved, the air pollution outputs would have the potential to be decreased by about 60% in the whole China. Conclusion Both environmental and technical efficiencies have the potential to be greatly improved in China, which may provide some advice for policy-makers.
文摘Envelope analysis is an effective method for characterizing impulsive vibrations in wired condition monitoring(CM)systems. This paper depicts the implementation of envelope analysis on a wireless sensor node for obtaining a more convenient and reliable CM system. To maintain CM performances under the constraints of resources available in the cost effective Zigbee based wireless sensor network(WSN), a low cost cortex-M4 F microcontroller is employed as the core processor to implement the envelope analysis algorithm on the sensor node. The on-chip 12 bit analog-to-digital converter(ADC) working at 10 k Hz sampling rate is adopted to acquire vibration signals measured by a wide frequency band piezoelectric accelerometer. The data processing flow inside the processor is optimized to satisfy the large memory usage in implementing fast Fourier transform(FFT) and Hilbert transform(HT). Thus, the envelope spectrum can be computed from a data frame of 2048 points to achieve a frequency resolution acceptable for identifying the characteristic frequencies of different bearing faults. Experimental evaluation results show that the embedded envelope analysis algorithm can successfully diagnose the simulated bearing faults and the data transmission throughput can be reduced by at least 95% per frame compared with that of the raw data, allowing a large number of sensor nodes to be deployed in the network for real time monitoring.
基金supported by the National Natural Science Foundation of China (70961005)211 Project for Postgraduate Student Program of Inner Mongolia University+1 种基金National Natural Science Foundation of Inner Mongolia (2010Zd342011MS1002)
文摘The conventional data envelopment analysis （DEA） measures the relative efficiencies of a set of decision making units with exact values of inputs and outputs. In real-world prob- lems, however, inputs and outputs typically have some levels of fuzziness. To analyze a decision making unit （DMU） with fuzzy input/output data, previous studies provided the fuzzy DEA model and proposed an associated evaluating approach. Nonetheless, numerous deficiencies must still be improved, including the α- cut approaches, types of fuzzy numbers, and ranking techniques. Moreover, a fuzzy sample DMU still cannot be evaluated for the Fuzzy DEA model. Therefore, this paper proposes a fuzzy DEA model based on sample decision making unit （FSDEA）. Five eval- uation approaches and the related algorithm and ranking methods are provided to test the fuzzy sample DMU of the FSDEA model. A numerical experiment is used to demonstrate and compare the results with those obtained using alternative approaches.
文摘The cylindrical worm processed by annular grinding wheel envelope in two degree of freedom motion state is a novel worm. This paper explains the shaping principle of such a worm. To improve meshing quality and the properties of contact and lubrication, the multi objective optimization has been conducted for the first time to the parameters of such a worm pair by the fuzzy optimal method. The results show that, the shape of the contact line is visibly more sloped than before being optimized, lubrication angle is apparently bigger, and the distribution of contact lines is much improved.
